\begin{tikzpicture}
    \tkzDefPoints{0/0/B, 3.5/0/C, 2.8/2/A}

    \tkzDrawPolygon(A,B,C)
    \tkzLabelSegment[below](B,C){$a$}
    \tkzLabelSegment[above right](A,C){$b$}
    \tkzLabelSegment[above left](A,B){$c$}
    \tkzLabelPoints[above](A)
    \tkzLabelPoints[left](B)
    \tkzLabelPoints[right](C)
\end{tikzpicture}

